Conventionally, wireless tire condition monitoring apparatuses have been proposed that permit the driver in the passenger compartment to check the conditions of the tires of a vehicle. One such tire condition monitoring apparatus includes a receiver mounted in a vehicle body and transmitters attached to respective wheel assemblies. Each transmitter detects the condition of the associated tire, that is, pressure and temperature in the tire, and wirelessly transmits a signal containing data that represents the detected tire condition. The receiver receives signals transmitted from the transmitters through a reception antenna, and displays information regarding the tire conditions on a display provided in the passenger compartment as necessary.
In such a tire condition monitoring apparatus, the receiver is preferably configured to determine which one of the wheel assemblies a received signal has been transmitted from, in other words, the position of the wheel assembly associated with the received signal.
In the tire condition monitoring apparatus disclosed in Patent Document 1, a transmitter is attached to each of the wheel assemblies of a vehicle. Each transmitter has an acceleration sensor. The transmitter transmits a signal based on the acceleration detected by the acceleration sensor at the time when the rotational position of the wheel assembly is at a constant position (for example, the lowest position). The receiver mounted on the vehicle body detects the rotational positions of the respective wheel assemblies at the time of reception of the signals from the transmitters. The receiver then identifies the positions of the wheel assemblies based on variation in the rotational positions of the wheel assemblies at the times of multiple receptions of the signals.